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A New Molecular Magnetic Semiconductor Based On Tetrathiafulvalene (ttf) And Oxamato Ligand (opba): [ttf]2[cu(opba)]·h2o
No full textAn oxamato-based compound of formula [ttf]2[Cu(opba)] ·H2O, with ttf = tetrathiafulvalene and opba = ortho-phenylenebis(oxamato), has been prepared and characterized. The complex was obtained by metathesis from (ttf)3(BF4)2 and (Bu4N)2[Cu(opba)] in acetonitrile at room temperature. The UV-Vis-NIR spectrum reveals the presence of the radical cation in two forms, (ttf•+) and (ttf•+)2 dimer. The electronic transport properties of [ttf]2[Cu(opba)]·H 2O were studied by impedance spectroscopy (IS) and linear voltammetry (LV), and show a typical semiconductor behavior. The EPR spectra exhibit two superposed lines corresponding to electron spins of CuII ions and ttf•+ radical cations. The dc magnetic properties show a room temperature value of the χMT product close to that expected for three uncoupled S = 1/2 spins and a value of 0.13 emu K mol-1 at low temperature (4 K). The χMT vs. T curve was fitted and the best model consists of a term for a (ttf•+)2 dimer (Bleaney-Bowers, leading to J2 = -186 cm-1) and a second term related to an antiferromagnetic {Cu...ttf•+} chain (J 1 = -10.1 cm-1).21712741282Wudl, F., Smith, G.M., Hufnagel, E.J., (1970) J. Chem. Soc. D, Chem. Commun., p. 1453Wudl, F., Wobschal, D., Hufnagel, E.J., (1972) J. Am. Chem. Soc., 94, p. 670Ferraris, J., Walatka, V., Perlstei, J., Cowan, D.O., (1973) J. Am. Chem. Soc., 95, p. 948Coronado, E., Day, P., (2004) Chem. Rev., 104, p. 5419Williams, J.M., Kini, A.M., Wang, H.H., Carlson, K.D., Geiser, U., Montgomery, L.K., Pyrka, G.J., Whangbo, M.H., (1990) Inorg. Chem., 29, p. 3272Wang, H.H., Schlueter, J.A., Geiser, U., Williams, J.M., Naumann, D., Roy, T., (1995) Inorg. Chem., 34, p. 5552Kahn, O., Stumpf, H., Pei, Y., Sletten, J., (1993) Mol. Cryst. Liq. Cryst., 233, p. 231Stumpf, H.O., Ouahab, L., Pei, Y., Grandjean, D., Kahn, O., (1993) Science, 261, p. 447Pereira, C.L.M., Doriguetto, A.C., Konzen, C., Meira-Belo, L.C., Leitao, U.A., Fernandes, N.G., Mascarenhas, Y.P., Stumpf, H.O., (2005) Eur. J. Inorg. Chem., p. 5018Pereira, C.L.M., Pedroso, E.F., Novak, M.A., Brandl, A.L., Knobel, M., Stumpf, H.O., (2003) Polyhedron., 22, p. 2387Dias, M.C., Knobel, M., Stumpf, H.O., (2001) J. Magn. Magn. Mater., 226, p. 1961Vaz, M.G.F., Knobel, M., Speziali, N.L., Moreira, A.M., Alcantara, A.F.C., Stumpf, H.O., (2002) J. Braz. Chem. Soc., 13, p. 183Vaz, M.G.F., Pedroso, E.F., Speziali, N.L., Novak, M.A., Alcantara, A.F.C., Stumpf, H.O., (2001) Inorg. Chim. Acta, 326, p. 65Cangussu, D., Nunes, W.C., Pereira, C.L.M., Pedroso, E.F., Mazali, I.O., Knobel, M., Alves, O.L., Stumpf, H.O., (2008) Eur. J. Inorg. Chem., p. 3802Pereira, C.L.M., Pedroso, E.F., Stumpf, H.O., Novak, M.A., Ricard, L., Ruiz-Garcia, R., Riviere, E., Journaux, Y., (2004) Angew. 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Cluster Glass-like Behavior In A 2d Bimetallic Molecule-based Magnet
No full textThe compound of formula Na2[Co2{Cu(opba)}3]·2DMSO ·6H2O has been synthesized where opba stands for orthophenylenebis(oxamato) and DMSO is dimethylsulfoxide. Magnetic properties have been investigated in the 2-300 K temperature range. The compound presents a large coercive field, around 3.5 kOe at 4.2 K, and the A.C. susceptibility measurements has revealed a cluster glass-like behavior. © 2003 Elsevier Science Ltd. All rights reserved.2214-1723872390Miller, J.S., Calabrese, J.C., Rommelmann, H., Chittipeddi, S.R., Zhang, J.H., Reiff, W.M., Epstein, A.J., (1987) J. Am. Chem. Soc., 109, p. 769Kahn, O., (1993) Molecular Magnetism, , Verlag-Chemie, New YorkDormann, J.L., Fiorani, D., Tronc, E., (1997) Adv. Chem. Phys., 98, p. 283Stumpf, H.O., Pei, Y., Kahn, O., Sletten, J., Renard, J.P., (1993) J. Am. Chem. Soc., 115, p. 6738Stumpf, H.O., Ouahab, L., Pei, Y., Grandjean, D., Kahn, O., (1993) Science, 261, p. 447Stumpf, H.O., Pei, Y., Michaut, C., Kahn, O., Renard, J.P., Ouahab, L., (1994) Chem. Mater., 6, p. 257Cador, O., Price, D., Larionova, J., Mathonière, C., Kahn, O., Yakhmi, J.V., (1997) J. Mater. Chem., 7, p. 1263Vaz, M.G.F., Pinheiro, L.M.M., Stumpf, H.O., Alcântara, A.F.C., Golhen, S., Ouahab, L., Cador, O., Kahn, O., (1999) Chem. Eur. J., 5, p. 1486Dias, M.C., Knobel, M., Stumpf, H.O., (2001) J. Mag. Magn. Mater., 226, p. 1961Kadam, R.M., Sastry, M.D., Bhide, M.K., Chavan, S.A., Yakhmi, J.V., Kahn, O., (1997) Chem. Phys. Lett., 281, p. 292Vaz, M.G.F., Pedroso, E.F., Speziali, N.L., Novak, M.A., Alcântara, A.F.C., Stumpf, H.O., (2001) Inorg. Chim. Acta, 326, p. 65Vaz, M.G.F., Knobel, M., Speziali, N.L., Moreira, A.M., Alcântara, A.F.C., Stumpf, H.O., (2002) J. Brazil Chem. Soc., 13, p. 183Surville-Barland, C., Ruiz, R., Aukaloo, A., Journaux, Y., Castro, I., Cervera, B., Julve, M., Sapinã, F., (1998) Inorg. Chim. Acta, 278, p. 159Ruiz, R., Surville-Barland, C., Journaux, Y., Colin, J.C., Castro, I., Cervera, B., Julve, M., Sapiña, F., (1997) Chem. Mater., 9, p. 201Pejakovic, D.A., Manson, J.L., Miller, J.S., Epstein, A.J., (2000) J. Appl. Phys., 87, p. 6028Van Koningsbruggen, P.J., Kahn, O., Nakatani, K., Pei, Y., Renard, J.P., Drillon, M., Legoll, P., (1990) Inorg. Chem., 29, p. 3325Mydosh, J.A., (1993) Spin Glasses: An Experimental Introduction, , Taylor & Francis, Londre
Magnetic Properties Of One-dimensional Cocu(opba) Systems And Dft Studies Of The Building Blocks
No full textThe synthesis of one-dimensional, molecule-based magnets and the investigation of their structure and physical properties are described. The one-dimensional CoCu(opba) system, where opba [ortho-phenylenebis(oxamato)] bridges the metal ions resulted in antiferromagnetic coupling, and was studied by insertion of electron donating and electron withdrawing groups in the organic ligands' aromatic rings. In order to verify the influence of these modifications, three compounds of the formula [CoCu(opba-xy)], where x=y=CH3 (compound 1), x=y=Cl (compound 2), x=H and y=NO2 (compound 3) are described. The electronic structure of the oxamato bridge group has been studied using calculations at the density functional theory (DFT) level for [Cu(opba-xy)]2- building blocks. Magnetic measurements in polycrystalline samples showed ferrimagnetic behavior for the three compounds. Least-squares fits of the experimental data indicate antiferromagnetic couplings JCoCu of -35.0, -32.9 and -24.2 cm-1 for 1, 2 and 3, respectively. © 2008 Elsevier B.V. All rights reserved.32014e200e203Pardo, E., Ruiz-Garcia, R., Lloret, F., Faus, J., Julve, M., Journaux, Y., Delgado, F., Ruiz-Perez, C., (2004) Adv. Chem. Mater., 16, p. 1597Pardo, E., Ruiz-Garcia, R., Lloret, F., Faus, J., Julve, M., Journaux, Y., Novak, M.A., Ruiz-Perez, C., (2007) Chem. Eur. J., 13, p. 2054Pereira, C.L.M., Pedroso, E.F., Stumpf, H.O., Novak, M.A., Ricard, L., Ruiz-Garcia, R., Rivière, E., Journaux, Y., (2004) Angew. Chem. Int. Ed., 43, p. 955Vaz, M.G.F., Knobel, M., Speziali, N.L., Moreira, A.M., Alcantara, A.F.C., Stumpf, H.O., (2002) J. Braz. Chem. Soc., 13, p. 183Pereira, C.L.M., Doriguetto, A.C., Konzen, C., Meira-Belo, L.C., Leitão, U.A., Fernandes, N.G., Brandl, A.L., Stumpf, H.O., (2005) Eur. J. Inorg. Chem., p. 5018Fettouhi, M., Ouahab, L., Boukhari, A., Cador, O., Mathonière, C., Kahn, O., (1996) Inorg. Chem., 35, p. 4932Kahn, O., (1993) Molecular Magnetism, , VCH, New YorkKoningsbruggen, P.J., Kahn, O., Nakatani, K., Pei, Y., Renard, J.P., Drillon, M., Legoll, P., (1990) Inorg. Chem., 29, p. 3325J.A. Pople, et al., Gaussian Inc., Pittsburgh, PA, 2003Gillon, B., (2002) Magnetism Molecules to Materials I: Models and Experiments, p. 356. , Miller J.S., and Drillon M. (Eds), Wiley-VCH, German
Soft And Hard Molecule-based Magnets Of Formula [bu4n] 2[m2{cu(opba)}3]. Dmf [m = Mn(ii) Or Co(ii), Opba = Ortho-phenylenebis(oxamato), Dmf = Dimethylformamide]
No full textThe compounds of formula [Bu4N]2[Mn 2{Cu(opba)}3] . 4DMF.5H2O (BMn) and [Bu 4N]2 [Co2{Cu(opba)}3]. DMF.H 2O (BCo) have been synthesized (opba = ortho-phenylenebis(oxamato)). BMn shows a spontaneous magnetization below a critical temperature Tc equal, to 22 K; for BCo, Tc = 40 K, the strongest for this type of system. While BMn is a soft magnet, BCo exhibits a coercive field, of 4kOe. © 2001 Elsevier Science B.V. All rights reserved.226-230PART II19611963Miller, J.S., Calabrese, J.C., Epstein, A.J., Bigelow, R.W., Zhang, J.H., Reiff, W.M., (1986) J. Chem. Soc. Chem. Commun., p. 1026Pei, Y., Verdaguer, M., Kahn, O., Sletten, J., Renard, J.-P., (1986) J. Am. Chem. Soc., 108, p. 7428Stumpf, H.O., Pei, Y., Kahn, O., Sletten, J., Renard, J.-P., (1993) J. Am. Chem. Soc., 115, p. 6738Stumpf, H.O., Pei, Y., Michaut, C., Kahn, O., Renard, J.-P., Ouahab, L., (1994) Chem. Mater., 6, p. 257Vaz, M.G.F., Pinheiro, L.M.M., Stumpf, H.O., Alcântara, A.F.C., Golhen, S., Ouahab, L., Cador, O., Kahn, O., (1999) Chem. Eur. J., 5, p. 1486Stumpf, H.O., (1993) Science, 261, p. 447Stumpf, H.O., (1994) J. Am. Chem. Soc., 116, p. 386
Slow Magnetic Relaxation In Coiicuii Coordination Oligomer Built Into Mesoporous Material
No full textThe ferrimagnetic system CoCu(opba) [opba = ortho-phenylenebis( oxamato)] was employed to prepare a traditional chain [CoCu(opba)]·4H2O (1) and a nanocomposite by incorporation in porous Vycor glass (PVG). This nanocomposite was made by first anchoring [Bu4N]2[Cu(opba) ] on PVG [PVG-Cu (2)] and then treating it "in situ" with cobalt(II) acetate to obtain the nanomagnet PVG-CuCo (3). Magnetic measurements show that 1 consists of a one-dimensional ferrimagnet with strong intrachain antiferromagnetic coupling and weak interchain interactions that result in spin-glass behavior below 3.5 K. Nanocomposite 3 presents ferrimagnetic chains limited by the nanopore size, which leads to a slow relaxation of the magnetization following Arrhenius' law, frequency dependence for in-phase and out-of-phase susceptibility, and hysteresis below the blocked regime temperature (< 6 K). These features are characteristics of single-chain magnets (SCM). © Wiley-VCH Verlag GmbH & Co. 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High Coercivity In A New Molecular Iron-based Magnet
No full textA new molecule-based magnet containing Fe(II), Fe(III) and Cu(opba)2- (opba = ortho-phenylenebis(oxamato)) was synthesized. The samples were characterized by infrared spectroscopy, elemental analysis, atomic absorption, macroscopic magnetometry, X-ray diffraction, and 57Fe Mössbauer spectroscopy. Magnetic measurements show that the compound presents a transition temperature below 15 K and a high coercivity, around 6.3 kOe at 4.2 K. At room temperature, the Mössbauer spectrum is dominated by a broad doublet characteristic of Fe(II), and a small fraction of Fe(III) ions is also identified. At 4.2 K, the spectrum shows clear magnetic splitting. © 2001 Elsevier Science Ltd.20Nov/1414311434Vaz, M.G.F., Pinheiro, L.M.M., Stumpf, H.O., Alcântara, A.F.C., Golhen, S., Ouahab, L., Cador, O., Kahn, O., (1999) Chem. Eur. J., 5, p. 1486Surville-Barland, C., Ruiz, R., Aukauloo, A., Journaux, Y., Castro, I., Cervera, B., Julve, M., Sapinã, F., (1998) Inorg. Chim. Acta, 278, p. 159Kahn, O., (1993) Molecular Magnetism, , Verlag-Chemie, New YorkTamaki, H., Zhong, Z.J., Matsumoto, N., Kida, S., Korkawa, M., Achiwa, N., Hashumoto, Y., Okawa, H., (1992) J. Am. Chem. Soc., 114, p. 6974Stumpf, H.O., Pei, Y., Kahn, O., Sletten, J., Renard, J.P., (1993) J. Am. Chem. Soc., 115, p. 6738Ruiz, R., Surville-Barland, C., Journaux, Y., Colin, J.C., Castro, I., Cervera, B., Julve, M., Sapinã, F., (1997) Chem. Mater., 9, p. 201Stumpf, H., Pei, Y., Ouahab, L., Berre, F.L., Codjovi, E., Kahn, O., (1993) Inorg Chem., 32, p. 5687Vaz, M.G.F., Stumpf, H., Ardisson, J.D., Macedo, W.A.A., (2001) J. Magn. Magn. Mater., , in pres
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A Crystalline Phase Transition And Optical Properties In A Co Iicuii Oxamato-bridged Ferrimagnetic Chain
No full textThe compound [CoCu(opba)(DMSO)3] (1) [opba = orthophenylenebis(oxamato)] has been synthesized and characterized. Its crystal structure has been analyzed by X-ray diffraction techniques at 100 and 298 K. A structural phase-transition has been detected at around 150 K. An orthorhombic crystalline system is found at both temperatures, with very similar unit-cell dimensions. At room temperature 1 crystallizes in the Pnam space group (α-1 phase), with a = 7.6712(2), b = 14.8003(3), c = 21.0028(5) Å, and Z = 4, whereas at low temperature it crystallizes in the Pna21 space group (β-1 phase), with a = 7.3530(2), b = 14.5928(4), c = 21.0510(7) Å, and Z = 4. Both crystalline phases consist of linearly ordered bimetallic chains with the [Cu(opba)]2- units tied by CoII ions to form a one-dimensional system. The DMSO molecules in α-1, which are coordinated to either CuII or CoII, are disordered. At low temperature, a small reorganization of the CuII and Co II environments is observed. The origin of this phase transition, which is completely reversible, is the modification of the crystalline packing with the temperature. Linear birefringence measurements were done on single crystals in the 100-300 K temperature range. Around 150 K, the linear birefringence curve shows an inflexion that is interpreted as being related to the conversion of α-1 into β-1. Both dc and ac magnetic measurements were performed on the polycrystalline sample. The results reveal a one-dimensional ferrimagnetic behavior. Single crystal optical characterization at room temperature shows that 1 presents a very strong dichroism superposed on the linear birefringence. © Wiley-VCH Verlag GmbH & Co. KGaA, 2005.2450185025Miller, J.S., Calabrese, J.C., Epstein, A.J., Bigelow, R.W., Zang, J.H., Reiff, W.M., (1986) J. Chem. Soc., Chem. Commun., pp. 1026-1028Pei, Y., Verdaguer, M., Kahn, O., Sletten, J., Renard, J.P., (1986) J. Am. Chem. Soc., 108, pp. 7428-7430Miller, J.S., Epstein, A.J., (1994) Angew. 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Soc., 13, pp. 183-189Pereira, C.L.M., Pedroso, E.F., Stumpf, H.O., Novak, M.A., Ricard, L., Ruiz-Garcia, R., Rivière, E., Journaux, Y., (2004) Angew. Chem. Int. Ed., 43, pp. 955-958Caneschi, A., Gatteschi, D., Lalioti, N., Sangregorio, C., Sessoli, R., Venturi, G., Vindigni, A., Novak, M.A., (2001) Angew. Chem. Int. Ed., 40, pp. 1760-1763noteNye, J.F., (1985) Physical Properties of CrystalsTheir Representation by Tensors and Matrices, , Oxford University PressOakberg, T., (1994) PEM-90TM Photoelastic Modulator User Manual, , Hinds Instruments, HillsboroKahn, O., (1993) Molecular Magnetism, , VCH, New YorkVan Koningsbruggen, P.J., Kahn, O., Nakatani, K., Pei, Y., Renard, J.P., Drillon, M., Legoll, P., (1990) Inorg. Chem., 29, pp. 3325-3331Turner, S., Kahn, O., Rombardel, L., (1996) J. Am. Chem. Soc., 118, pp. 6428-6432Carlin, R.L., (1986) Magnetochemistry, , Springer-Verlag, BerlinBlessing, R.H., (1995) Acta Crystallogr., Sect. A, 51, pp. 33-38Sheldrick, G.M., (1997) SHELXS-97. 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Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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